3.1 Cell Theory
KEY CONCEPT Cells are the Basic unit of life.
3.1 Cell Theory
The cell theory grew out of the work of many scientists
and improvements in the microscope.
3.1 Cell Theory
3.1 Cell Theory
3.1 Cell Theory
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The Cell theory has three principles.
1. All organisms are made of cells.
3.1 Cell Theory
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The Cell theory has three principles.
1. All organisms are made of cells.
2. All existing cells are produced by other living cells.
3.1 Cell Theory
The Cell theory has three principles.
1. All organisms are made of cells.
2. All existing cells are produced by other living cells.
3. The cell is the most basic unit of life.
3.1 Cell Theory
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All cells share certain characteristics.
3.1 Cell Theory
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All cells share certain characteristics.
1. Cells tend to be microscopic.
Bacterium
(colored SEM; magnification 8800x)
3.1 Cell Theory
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All cells share certain characteristics.
1. Cells tend to be microscopic.
2. All cells are enclosed
by a membrane.
cell membrane
Bacterium
(colored SEM; magnification 8800x)
3.1 Cell Theory
•
All cells share certain characteristics.
1. Cells tend to be microscopic.
2. All cells are enclosed
by a membrane.
3. All cells are filled with
cell membrane
cytoplasm.
cytoplasm
Bacterium
(colored SEM; magnification 8800x)
3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
3.1 Cell Theory
3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Eukaryotic cells have a
nucleus.
nucleus
cell membrane
3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Eukaryotic cells have a
nucleus.
nucleus
• Eu = true
• Karyote = nucleus
• Eukaryotic cells have
membrane-bound organelles.
• Ex: All animals & plants
organelles
• Some single celled organisms
cell membrane
3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Prokaryotic cells do not
have a nucleus.
nucleus
organelles
cell membrane
3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Prokaryotic cells do not
have a nucleus.
nucleus
• Prokaryotic cells do not
have membrane-bound
organelles.
• Ex: bacteria
organelles
cell membrane
cytoplasm
3.1 Cell Theory
Differences between cells
Size – limited by ratio between their outer surface
area & their volume
Shape – diversity of form reflects a diversity of
function
Internal Organization – organelles – perform specific
functions for the cell
3.3 Cell Theory
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3.3 KEY CONCEPT The cell membrane is a barrier that
separates a cell from the external environment.
3.3
3.3 Cell Theory
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The cell membrane has two major functions.
– forms a boundary between inside and outside of the
cell
– controls passage of materials
cell membrane
3.3 Cell Theory
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Homeostasis
• Cell membrane maintains a stable internal environment
inside the cell by allowing some molecules to pass
through and not others
• Selectively Permeable
3.3 Cell Theory
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The cell membrane is selectively permeable.
Some molecules can cross the membrane
while others cannot.
3.3 Cell Theory
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The cell membrane is selectively permeable.
Some molecules can cross the membrane
while others cannot.
3.3 Cell Theory
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Cell membranes are composed of two phospholipid
layers.
• polar head (hydrophilic – likes water)
• 2 nonpolar tails (hydrophobic – repelled by water)
3.3 Cell Theory
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Cell Membrane –Fluid Mosaic Model – constant
motion
•
•
the phospholipids move within the membrane
Proteins in the membrane also move like boats
Peripheral proteins – found on the inside &
outside of the cell
Integral proteins – extend through membrane
3.3 Cell Theory
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Chemical signals are transmitted across the cell
membrane.
• Receptors bind with ligands and change shape.
• There are two types of receptors.
3.3 Cell Theory
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Chemical signals are transmitted across the cell
membrane.
• Receptors bind with ligands and change shape.
• There are two types of receptors.
– intracellular receptor
3.3 Cell Theory
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Chemical signals are transmitted across the cell
membrane.
• Receptors bind with ligands and change shape.
• There are two types of receptors.
– intracellular receptor
– membrane receptor
3.3 Cell Theory
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3.2 Cell Theory
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3.2 KEY CONCEPT Eukaryotic cells share many
similarities.
3.2 Cell Theory
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Cells have an internal structure.
3.2 Cell Theory
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Cells have an internal structure.
• The cytoskeleton has many functions.
3.2 Cell Theory
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Cells have an internal structure.
• The cytoskeleton has many functions.
– supports and shapes cell
3.2 Cell Theory
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Cells have an internal structure.
• The cytoskeleton has many functions.
– supports and shapes cell
– helps position and transport organelles
3.2 Cell Theory
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Cells have an internal structure.
• The cytoskeleton has many functions.
– supports and shapes cell
– helps position and transport organelles
– provides strength
3.2 Cell Theory
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Cells have an internal structure.
• The cytoskeleton has many functions.
– supports and shapes cell
– helps position and transport organelles
– provides strength
– assists in cell division
3.2 Cell Theory
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Cells have an internal structure.
• The cytoskeleton has many functions.
– supports and shapes cell
– helps position and transport organelles
– provides strength
3.2 Cell Theory
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Centrioles are tubes found in the centrosomes
(cytoskeleton)
3.2 Cell Theory
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Centrioles are tubes found in the centrosomes.
– Centrioles help divide
DNA.
3.2 Cell Theory
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•
Centrioles are tubes found in the centrosomes.
– Centrioles help divide
DNA.
– Centrioles form cilia and
flagella.
Cilia & flagella assist in movement and feeding
– Cilia – short, numerous hair-like extensions
– Flagella – longer, move with a whip-like motion – cell
usually only has 1 or 2
3.2 Cell Theory
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The nucleus stores genetic information.
3.2 Cell Theory
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Nucleus
Nuclear matrix – nucleus skeleton
Nuclear envelope – double membrane
Chromatin – strands of DNA
Chromosomes – formed from chromatin during cell
division
Nuclear pores – small holes in the nuclear envelope
Nucleolus – site where ribosomes are formed
3.2 Cell Theory
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3.2 Cell Theory
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Endoplasmic reticulum.
– Series of highly folded membranes
3.2 Cell Theory
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There are two types of endoplasmic reticulum.
3.2 Cell Theory
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There are two types of endoplasmic reticulum.
1. rough endoplasmic
reticulum
• covered in ribosomes
makes proteins for use
outside of the cell
3.2 Cell Theory
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There are two types of endoplasmic reticulum.
1. rough endoplasmic
reticulum
2. smooth endoplasmic
reticulum
• makes and
stores steroids (lipids)
•
3.2 Cell Theory
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Ribosomes link amino acids to form proteins.
Free floating ribosomes make proteins for use inside of
the cell
3.2 Cell Theory
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Vesicles are membrane-bound sacs that hold materials.
Found in animal cells
3.2 Cell Theory
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Vacuoles are fluid-filled sacs that hold materials.
Found in plant cells
3.2 Cell Theory
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Mitochondria supply energy to the cell.
3.2 Cell Theory
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Mitochondria – sites of
chemical reactions
transfer Energy (E)
from organic
compounds (food) into
ATP (cellular E)
Cell respiration
-Cristae – folded inner
membrane
-Increases the surface
area
-Increases E production
3.2 Cell Theory
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3.2 Cell Theory
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Golgi Apparatus – processes,
packages, & secretes substances
3.2 Cell Theory
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Lysosomes contain enzymes to digest unwanted or
broken material.
3.2 Cell Theory
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Plant cells have cell walls and chloroplasts.
3.2 Cell Theory
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Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
3.2 Cell Theory
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3.2 Cell Theory
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Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
• Chloroplasts convert solar energy to chemical energy
(photosynthesis)
• Thylakoids – stacks of sacs filled with chlorophyll
Increase surface area - increase photosynthesis
3.2 Cell Theory
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